A new prospective study has validated the newly adopted American Thyroid Association (ATA) sonographic pattern risk assessment for selection of thyroid nodules undergoing ultrasound-guided fine needle aspiration (FNA) based upon Bethesda cytology and surgical pathology results. In addition, the study validates that cytological indeterminate nodules with an ATA high-risk sonographic pattern have a high likelihood of being malignant.

The findings, which were reported at the 86th Annual Meeting of the ATA, are reassuring for clinicians. The investigators examined the ATA sonographic pattern risk assessment (high, intermediate, low, and very low) of 211 thyroid nodules. All the nodules were selected for ultrasound-guided FNA, with evaluation of the results based on the Bethesda System for Reporting Thyroid Cytopathology. The researchers also looked separately at the surgical pathology results for the subset undergoing surgical excision.

“I was pleasantly surprised because it confirmed the risk estimates that the ATA had proposed in the recent guidelines published in January. So, we prospectively validated those recommendations,” said study investigator David Steward, MD, professor of otolaryngology–head and neck surgery at the University of Cincinnati in Ohio.

He said traditionally nodules were biopsied based on their size. While nodule size is still incorporated into the equation, clinicians now take into account sonographic assessment of the nodule.

The study included 199 patients and approximately three-fourths were women (157 women and 42 men). The 211 thyroid nodules averaged 2.4 cm in size (range, 1–7 cm). The investigators used the ATA ultrasound pattern risk assessment and the nodules were classified as high risk (4%), intermediate risk (31%), low risk (38%), or very low risk (26%) of malignancy.

The researchers found that the size of the nodules selected for ultrasound-guided FNA was inversely correlated with sonographic risk assessment. Specifically, they found that lower-risk nodules were larger on average, consistent with the ATA guidelines recommendation to only biopsy nodules with sonographically low- or very low-risk patterns if they are large.

In addition, results showed that the malignancy rates determined from cytology or permanent pathology varied significantly by ATA sonographic risk. For high-risk and intermediate-risk nodules, the rates were 100% and 17%, respectively. The rates were 12% for low-risk and 1% for very low-risk nodules. These are similar to the ATA estimated risks of 70% to 90% for high, 10% to 20% for intermediate, 5% to 10% for low, and less than 3% for very low risk.

The study also demonstrated that the distribution of Bethesda cytology classification varied significantly by ATA ultrasound pattern risk assessment. The high-risk nodules were 77% malignant or suspicious for malignancy and 22% atypical. For intermediate-risk nodules, 6% were malignant or suspicious for malignancy, 30% were atypical, 8% were follicular or Hürthle neoplasm, 47% were benign, and 9% were nondiagnostic. For the low-risk nodules, 1% were malignant or suspicious for malignancy, 25% were atypical or a follicular lesion of undetermined significance, 5% were follicular or Hürthle neoplasms, 61% were benign, and 8% were nondiagnostic. For the very low-risk nodules, 30% were deemed atypical or follicular lesions of undetermined significance and 70% were benign.

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In their analysis, the researchers found that the malignancy rates of atypical cytological indeterminate nodules surgically excised also varied significantly by ATA sonographic risk. Rates were 100% and 21% for high- and intermediate-risk nodules, respectively, and 17% and 12% for low- and very low-risk nodules, respectively.

“It is not the first study to show the high positive predictive value of a high-risk sonographic pattern in cytological atypical indeterminate nodules, but it prospectively confirms the ATA guidelines recommendations,” Dr Steward told Endocrinology Advisor.

“It is important to have this knowledge that the sonographic pattern of the nodule will accurately stratify risk of malignancy from high to intermediate, low, and very low categories as suggested by the ATA guidelines so that physicians can inform patients of the likelihood of their nodule being benign or malignant based on the ultrasound and make an informed decision about whether to undergo needle biopsy,” he noted. “Further, if the biopsy is performed and comes back indeterminate for malignancy the sonographic risk assessment can help decision-making regarding possibly proceeding with surgery.”